Probing the Limits of Ligand Steric Bulk: Backbone CH Activation in a Saturated N‐Heterocyclic Carbene. Issue 13 (24th February 2014)

• Record Type: Journal Article
• Authors: Phillips, Nicholas; Tirfoin, Remi; Aldridge, Simon
• Is Part Of: Chemistry. Volume 20:Issue 13(2014)
• Page Start: 3825
• Page End: 3830
• Publication Date: 2014-02-24
• Subjects: Chemistry -- Periodicals; 540
• DOI: 10.1002/chem.201304243
• Languages: English
• ISSNs: 0947-6539

Abstract

<abstract abstract-type="main" xml:lang="en"> <title>Abstract</title> <p>The consequences of extremely high steric loading have been probed for late transition metal complexes featuring the expanded ring N‐heterocyclic carbene 6‐Dipp. The reluctance of this ligand to form 2:1 complexes with d‐block metals (rationalised on the basis of its percentage buried volume, % <italic>V</italic>_bur, of 50.8 %) leads to CH and CN bond activation processes driven by attack at the backbone β‐CH₂ unit. In the presence of Ir^I (or indeed H⁺) the net result is the formation of an allyl formamidine fragment, while Au^I brings about an additional ring (re‐)closure step via nucleophilic attack at the coordinated alkene. The net transformation of 6‐Dipp in the presence of [(6‐Dipp)Au]⁺ represents to our knowledge the first example of backbone CH activation of a saturated N‐heterocyclic carbene, proceeding in this case via a mechanism which involves free carbene in addition to the Au^I centre.</p> </abstract>